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The POST code checkpoints are the largest set of checkpoints during the BIOS
pre-boot process. The following table describes the type of checkpoints that may
occur during the POST portion of the BIOS:
Disable NMI, Parity, video for EGA, and DMA controllers. Initialize BIOS,
POST, Runtime data area. Also initialize BIOS modules on POST entry and
GPNV area. Initialized CMOS as mentioned in the Kernel Variable
Check CMOS diagnostic byte to determine if battery power is OK and
CMOS checksum is OK. Verify CMOS checksum manually by reading
storage area. If the CMOS checksum is bad, update CMOS with power-on
default values and clear passwords. Initialize status register A.
Initializes data variables that are based on CMOS setup questions.
Initializes both the 8259 compatible PICs in the system
Initializes the interrupt controlling hardware (generally PIC) and interrupt
Do R/W test to CH-2 count reg. Initialize CH-0 as system timer. Install the
POSTINT1Ch handler. Enable IRQ-0 in PIC for system timer interrupt.
Traps INT1Ch vector to “POSTINT1ChHandlerBlock.”
Initializes the CPU. The BAT test is being done on KBC. Program the
keyboard controller command byte is being done after Auto detection of
KB/MS using AMI KB-5.
Early CPU Init Start — Disable Cache - Init Local APIC
Set up boot strap proccessor Information
Set up boot strap proccessor for POST
Enumerate and set up application proccessors
Re-enable cache for boot strap proccessor
Early CPU Init Exit
Initializes the 8042 compatible Key Board Controller.
Detects the presence of PS/2 mouse.
Detects the presence of Keyboard in KBC port.
Testing and initialization of different Input Devices. Also, update the Kernel
Variables. Traps the INT09h vector, so that the POST INT09h handler gets
control for IRQ1. Uncompress all available language, BIOS logo, and Silent
Early POST initialization of chipset registers.
Uncompress and initialize any platform specific BIOS modules.
Initialize System Management Interrupt.
Initializes different devices through DIM.
See DIM Code Checkpoints section of document for more information.
Initializes different devices. Detects and initializes the video adapter
installed in the system that have optional ROMs.
Initializes all the output devices.
Allocate memory for ADM module and uncompress it. Give control to ADM
module for initialization. Initialize language and font modules for ADM.
Activate ADM module.
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